(i) Technical Field
The present invention relates to a method for producing a light-emitting device.
(ii) Related Art
Vertical cavity surface emitting lasers have been used as a light source for electronic apparatuses and the like because they are capable of emitting laser beams in a direction perpendicular to a substrate and an array is easily formed by two-dimensional integration. Such vertical cavity surface emitting lasers are applicable to, for example, light sources for forming latent images on a photosensitive member incorporated in a printer, light sources for optical communications, and light sources for optical mice.
Typical vertical cavity surface emitting lasers include a pair of distributed Bragg reflectors (DBRs) disposed on a semiconductor substrate, an active layer disposed between the pair of DBRs, and a cavity spacer layer. When an electric current is injected into the active layer through electrodes disposed on outer sides of the DBRs, lasing occurs in a direction perpendicular to the substrate. Many of vertical cavity surface emitting lasers currently put to practical use include an oxide confinement layer formed by performing steam oxidation on an AlAs or AlGaAs layer having a high Al content for the purpose of decreasing the threshold of electric current and controlling transverse modes. Such a vertical cavity surface emitting laser is referred to as an oxidized vertical cavity surface emitting laser. Many crystal defects generated by distortion due to oxidation are present in semiconductor crystals near the AlAs or AlGaAs layer that has been subjected to steam oxidation.
In oxidized vertical cavity surface emitting lasers, even when the same electric current is injected, the optical output decreases as the operating time increases. One of the causes of the degradation is as follows. Dislocation caused from crystal defects in the oxide confinement layer grows to an active layer in a light-emitting region using energy that comes from heat generated and electric current supplied during driving of the device, which prevents the active layer from emitting light.